The present invention relates to a ball-screw mechanism, and more particularly, to an improved ball-screw mechanism which is easily assembled and of compact design.
Presently, the ball return means in known ball-screw mechanisms consists of either an external return tube or a helical return guideway. The external return tube consists of some form of tubular ball catching member which conveys the ball from one end of the ball race back to the other. The tubes are located externally and are bolted onto the mechanism with clips and screws. This external hardware is, obviously, quite susceptible to damage from a variety of sources and is relatively expensive to fabricate. The extra hardware required to support the tube also defeats any compactness which may be required, such as in integral power stearing gears.
The helical return guideway as shown in my U.S. Pat. No. 3,826,153 avoids the problems of the external return tube. Although the helical return guideway provides significant improvements, continued research and development has shown particular aspects that may be further improved. The helical return guideway requires more bearing members due to the increased return path length. It also requires machining of end discs to transfer the balls into the return race. The helical return further requires a loading sleeve for loading the bearing members and a threaded locking member to hold the machined parts in place.
The present invention alleviates these requirements by utilizing unique fabricated parts which require no bolts, clips, or screws for assembly. Since all of the parts of the present invention interfit with each other, there is no need for any additional hardware and the mechanism is easily assembled.
Because the return tube of the present invention takes a more direct route than the helical guideway, fewer bearing members are required and, thus, the invention is more economical and durable. Furthermore, the bearing members of the present invention may be loaded directly into the return tube without the necessity of a loading sleeve or other apparatus. This obviously increases the efficiency and economy of assembling the mechanism.
By eliminating the need for external parts, the present ball-screw mechanism provides a compact design. Such a compact design makes the present invention ideal for use in steering gear pistons, as well as any other application where compactness and smooth operation must be combined with reliability. This invention, therefore, broadly concerns a compact ball-screw mechanism capable of smooth, reliable operation under a wide range of conditions.